Studying American shad

UPPER DELAWARE REGION — A low fog settles over the Delaware River as dusk begins its descent on October 15. Humans clad in waders and sporting headlamps arrange equipment along the shoreline as others board a boat. A long heavy net stretches between them. As the light fades, the seining begins, with representatives of several agencies working to determine the current health of American shad populations in the non-tidal Delaware River.

Seining [pronounced: say-ning] is the act of capturing fish using a weighted net that hangs vertically in the water. The National Park Service (NPS) has been performing the sampling this fall in conjunction with Pennsylvania Fish and Boat Commission (PAFBC) and Delaware Water Gap resource management professionals.

According to NPS biologist Jamie Myers, the goal is to develop protocols for monitoring young-of-the-year (YOY) American shad to ensure that populations are maintained or increased. Shad play a major role in the Delaware River ecosystem by providing an important food source for invertebrates, fishes, mergansers, bald eagles and osprey. They are also an important game fish and contribute significantly to cultural and recreational values.

A coast-wide assessment of American shad completed by the Atlantic States Marine Fisheries Commission (ASMFC) reported that the Delaware River populations had declined substantially since the early 1990s. It identified monitoring of YOY American shad production as a critical data need. The project will provide data about the distribution and relative annual abundance of YOY shad in the non-tidal nursery waters of the Delaware River and is a necessary first step to assessing their sustainability.

Results will be shared with the U.S. Fish and Wildlife Service and natural resource management agencies of New York, Pennsylvania, New Jersey and Delaware, which manage the shad population cooperatively through the Delaware River Basin Fish and Wildlife Cooperative (the Co-op).

The Co-op recently submitted a Draft American Shad Sustainability Plan to the ASMFC. According to the plan, if Delaware River YOY populations fall below a specified benchmark level, harvest may be further restricted or prohibited and other protective management options explored.

During the regional study, five sites were sampled in August, September and October, including Trenton and Phillipsburg in New Jersey and the Delaware Water Gap, Milford and Lackawaxen in Pennsylvania. Monthly totals for August were 10,973; for September were 11,177 and for October were 2,777 resulting in a total of 24,933 American shad YOY.

Unusually cold temperatures during the second weekend in October resulted in migration to warmer waters, with only 51 shad sampled at Milford Beach on October 12, down from 5,800 when the same site was sampled in August. Three nights later, only six shad were retrieved at the seining site near the Zane Grey Museum in Lackawaxen, PA.

So far, the counts look promising. “The low numbers aren’t indicative of a drop in the population, but rather what we would expect to see with the change in weather and water temperatures,” explains Myers. “After the high numbers we had in August and September, the population index was shaping up to be the third best overall index for non-tidal sampling done from 1981 to present, and the September 2012 index was the second best September ever. With the addition of our October hauls and the drop-off that we saw due to colder water temperatures, it dropped the 2012 index to being ninth-highest overall (from 1981 to present).”

About American shad:
American shad are an anadromous species indigenous to the Delaware River and the entire Atlantic Coast. Each spring, adults return to their natal waters to spawn. YOY shad remain in the river through summer and migrate downstream and out of the river in the fall. In the Delaware River, spawning occurs throughout the upper 318 km of non-tidal waters, which extend from Trenton, NJ to Hancock, NY. Three national parks encompass 77% of these waters. Maintaining viable populations is essential to the ecosystems of the Lower Delaware National Wild and Scenic River (LODE), Delaware Water Gap National Recreational Area (DEWA) and Upper Delaware Scenic and Recreation River (UPDE). In the 1890s, the Delaware River had the largest shad harvest of any river along the Atlantic Coast. Factors responsible for the current decline are unknown, but could include riverine habitat change, increased predation and excessive fishing-related mortality on adults. A monitoring program will also help to determine if shad populations are affected by reservoir releases.